Temperature-dependent switching device

ABSTRACT

A temperature-dependent switching device for cooperation with an electric switch and preferably constructed as a defrosting thermostat for refrigerators. A resilient bimetallic element is arranged in a sealed housing and acts upon the operating rod of a microswitch which is preferably constructed as a snap-action switch. The bimetallic element carries a weight which deflects said element more or less in accordance with the adjustable angular position of the housing.

United States Patent lnventor Appl. No. Filed Patented Priority Armand Bracht No. 18, Rue'Gerardmer, Mulhouse- Bourtzwiller, France Feb. 20, 1970 Jan. 4, 1972 Feb. 26, 1969 Germany TEMPERATURE-DEPENDENT SWITCHING [56] References Cited UNITED STATES PATENTS 3,529,105 9/1970 Huffman 337/365 X 2,885,504 5/1959 Yurtz ZOO/61.49 2,691,129 10/1954 Hall 337/53 X 1,645,290 10/1927 Mottlau 337/343 X Primary Examiner-Bernard A. Gilheany Assistant Examiner-Dewitt M. Morgan Attorney-Michael S. Striker ABSTRACT: A temperature-dependent switching device for cooperation with an electric switch and preferably constructed as a defrosting thermostat for refrigerators. A resilient bimetallic element is arranged in a scaled housing and acts upon the operating rod of a microswitch which is' preferably constructed as a snap-action switch. The bimetallic element carries a weight which deflects said element more or less in accordance with the adjustable angular position of the housing.

1 TEMPERATURE DEPENDENT SWITCHING DEVICE BACKGROUND OF THE INVENTION This invention relates to switching devices, and more specifically to a temperature-dependent switching device which is provided with a bimetallic element, cooperates with an electric switch and is preferably constructed as a defrosting thermostat for refrigerators.

SUMMARY OF THE INVENTION It is the object of the invention to provide a switching device which is simple in construction, largely insensitive to trouble due to freezing andwhich is controllable in a simple manner.

To attain this object the present invention provides a switching device of the type specified which comprises a housing haying closed sidewalls, a top wall therefor, and a bottom wall; a resilient bimetallic element arranged in said housing; an operating rod cooperating with said bimetallic element; a microswitch cooperating with said operating rod and constructed as a snap-action switch; and a weight carried by the resilient bimetallic element and adapted to deflect said element more or less in accordance with the adjustable angular position of the housing.

Readjustment of the upper and lower temperature values for switching on and switching off by means of the switching device is accomplished by the weight which, depending on its position relative to the fastening point or points of the elastic bimetallic element, more m les elastically bends the bimetallic element due to its gravity and thereby influences the microswitch correspondingly. By a definite mounting position of the switching device in a refrigerator thus fixed upper and lower temperature values are preset for changing over.

Advantageously, the housing is of watertight and airtight construction so that the components in the housing cannot oxidize due to atmospheric moisture and all movable parts and contact surfaces are prevented from freezing fast.

At least one wall of the housing may have an elastic diaphragm which preferably consists of rubber. This diaphragm can, with the housing being closed, yield to any differences in air pressure between the interior of the housing and the surrounding atmosphere which may arise due to differences in temperature. In this manner sealing spots of the housing are prevented from being constantly loaded and becoming untight in the course of time.

BRIEF DESCRIPTION OF THE DRAWING A preferred embodiment of the invention will now be described by way of exampleand with reference to the accompanying drawing, in which:

FIG. 1 is a, longitudinal section of a housing of a switching device according to the invention;

FIG. 2 is a section, on a reduced-scale, on the line II-Il of FIG. 1, and

FIG. 3 is a schematic elevational view of the switching device in aposition turned through 90 withrespect to FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a switching device which is accommodated in an elongatedhousing 1 made of brass, only one of the opposite ends of the housing 1, being closed by an end wall la. In the housing 1 a slide member is inserted which is of U-shaped cross section on the line A-A of FIG. 1. The slide member preferably likewise made of brass consists of a backplate 40 (see also FIG. 2), an impact plate 42 engaging the end wall la and a mounting plate 41 opposite the impact plate 42 respectively projecting forwardly from opposite side edges of the backplate. The mounting plate 41 extends approximately only over half the height of the back plate 40.

The slide member carries the essential component parts of the switching device, namely a pack of elastic strips 4 of bimetal and a microswitchi2. Due to this construction oflthe slide member the component parts can easily be fitted thereto outside the housing 1 and the slide member then be pushed into the housing 1 where it is seated substantially without play.

The bimetallic strips 4 are bent substantially into L-shape and provided at one end with aligned bores. Through these bores a fixing bolt 12 is passed which extends through a hole in the mounting plate 41 and onto which a nut 13 is screwed for clamping the bimetallic strips 4 together. In addition to the fixing bolt 12 and its nut 13, the bimetallic strips 4 are held together by a sleeve 10 to form the pack. The sleeve 10 is rigidly connected to the lowermost bimetallic strip 40 so that the bimetallic strips 4 can relatively move in their longitudinal direction. For the same reason a weight 5 in the form of a square metallic block is only secured to the free end of the farthest projecting bimetallic strip 40, the free ends of the other bimetallic strips 4 being somewhat spaced from the weight 5.

Adjacent the fixing bolt 12 a setscrew 9 is screwable in a hole in the mounting plate 41 to act upon the pack of bimetallic strips 4. With its end remote from the bimetallic strips 4 the setscrew 9 projects into a rubber plate 25. Prior to applying the rubber plate 25 by vulcanizing, the setscrew 9 is adjustable during the manufacture of the switching device so that the desired position of the bimetallic strips 4 can easily be adjusted. The subsequently applied rubber plate 25 closes the open end face of the housing 1 and simultaneously retains the fixing bolt 12 and especially the setscrew 9 in the once adjusted position. The rubber plate 25 makes a special locking of the slide member unnecessary.

The rubber plate 25 makes the housing 1 of the switching device watertight and airtight and is supported by the mounting plate 41 of the slide member. The rubber plate 25 bridges without any support the region between the mounting plate 41 and the bottom wall 1b of the housing. In this region an electric cable 3 is passed through the rubber plate 25 so as to be sealed therein and at the same time the rubber plate constitutes in this region an elastic diaphragm which is able to yield and thus to equalize pressure differences in the case when such pressure differences between the interior and exterior of the housing 1 occur. This equilization of pressure prevents sealing surfaces between the housing 1 or the cable 3 and the rubber plate 25 from being loaded over a relatively long period of time.

Differing from the embodiment shown in FIG. 1, equalization of pressure may also be achieved by constructing one of the housing walls in the form of a flexible metal foil under which preferably a perforated supporting wall may be placed for taking up heavy loads.

The cable 3 establishes electrical connection to the microswitch 2 and leads to an electric control device, not shown, which is located outside the housing 1 and associated with a refrigeration unit. The microswitch 2 is affixedto an angular holding strip 26 which is connected to the back plate 40 of the slide member. Conductors 3a and 3b of the cable 3' are each soldered to one of two fixed contacts 27 and 28 ofthe microswitch 2, whereas a third conductor 30 leads to an-electrically conductive support 29 on'which a resiliently swingable contact arm 30 is arrar'iged. The contact-arm 30isacted upon by a leaf spring 31 which imparts to the microswitch 2 the property of an electric quickaction known per se.

The contact arm 30 of the microswitch 2 cooperates with the T-shaped end of an operating rod 14 of insulating plastics material which is swingable by elastic bending properties of its shank portion secured at its other end to theholding strip 26. The T-shaped end of the operating rod 14 bears against the sleeve 10 from below.

The operation of the switching device according to the'invention is as follows:

In the case of a change in temperature the deflection of the bimetallic strips 4 varies, the pressure exerted by the strips4' on the operating rod 14 of thernicroswitch 2 increasing or decreasing as the case may be. This pressure is transmitted by the operating rod 14 to the contact arm 30. The contactarm 30 of the microswitch 2 is of the snapaction type and snaps over from one switch position into the other when the operating rod 14 has reached a predetermined position. Apart from the temperature the deflection of the bimetallic strips 4 is also influenced by the weight 5 which constantly intends to move downwards under gravity in the direction of the arrow Pf] and which, with the switching device in the position shown in FIG. 1, increases the deflection of the strips 4 and thus the' pressure acting on the operating rod 14.

FIG. 3 shows that by angularly turning the switching device through approximately 90 with respect to FIG. 1, the influence of the weight 5 on the deflection of the strips 4 has changed. In the position of the switching device shown in FIG. 3, with the force of gravity acting on the weight 5 in the direction of the arrow Pf2, the additional bending force acting on the strips 4 is substantially reduced and the changeover temperature is different from that resulting from the position of the device shown in FIG. 1. In this manner, the upper and lower temperature values at which a changeover operation in the microswitch 2 is released can be adjusted by simply turning the switching device and without the necessity of opening the housing 1 of the switching device. It is particularly advantageous that the difference between upper and lower changeover temperature values remains substantially constant.

As shown in FIG. 3, the housing 1 has a lever arm 20 attached thereto which is connected at its free end to a bushing 21. Into this bushing 21 the cable 3 is passed in the direction of view by bending it through 90 with respect to the shown cable portion. The housing 1 can be readily installed in a refrigerator so as to be slewable about the axis of the bushing 21 in the direction of the double arrow Pf3.

The switching device may be preferably constructed as a turning handle D which can be installed in a refrigerator provided with a nonrotatable scales on which the changeover temperatures of individual switch positions are indicated. The setting of the temperature difference by adjusting the setscrew 9 is normally made by the manufacturer, it can, however, also be performed subsequently when in special cases the setscrew 9 has been made accessible from outside through a bore or the like in the rubber plate 25.

A region 35 indicated by dash lines in FIG. 1 and covering part of the microswitch 2 and the end of the cable 3 as well as the conductors 3a, 3b and 3c is filled with a dielectric synthetic resin material. This synthetic resin material which may also be an adhesive protects the soldered joints at the ends of the conductors 3a, 3b and 3c. When a synthetic resin adhesive is used, the microswitch 2 and the cable 3 are hereby secured to the backplate 40.

The procedure of assembling the switching device is performed in air containing as little moisture as possible. When the housing 1 is hermetically sealed by the rubber plate 25, no moisture can penetrate the interior of the housing during operation of the switching device so that a long service life is ensured.

What is claimed is:

1. An adjustable thermostat device for refrigerators or the like comprising a closed housing; elongated bimetal means fixedly mounted at one end thereof in said housing; a weight attached to said elongated bimetal means spaced from one end of the latter; microswitch means arranged in said housing and having an operating portion adapted to be engaged by said bimetal means intermediate the ends of the latter so as to be actuated during curving of said bimetal means under the influence of temperature variations; and means mounting said housing turnably about an axis extending transverse to the elongation of said elongated bimetal means so that the component of said weight influencing the curvature of said bimetal means may be varied depending on the turned position of said housing, whereby the temperature at which said microswitch means is actuated may be varied by turning said housing about said axis.

2. A device as defined in claim I, wherein said bimetal means comprises at least one elongated resilient bimetallic strip fixedly attached at one end thereof to said housing and carryin said weight on the other end thereof.

3. A evice as claimed in claim 2, wherein several bimetallic strips are held together by a sleeve so as to be relatively movable in their longitudinal direction, one of said strips projecting beyond the other bimetallic strips and connected at its other end to the weight.

4. A device as claimed in claim 2, wherein asetscrew is arranged for cooperation with the resilient bimetallic strip and said strip is bent at the attachment end.

5. A device as claimed in claim 4, wherein the setscrew with its end remote from the bimetallic strip is nonrotatably held in a rubber plate forming one of the housing walls.

6. A device as claimed in claim 1, wherein the housing is of watertight and airtight construction.

7. A device as claimed in claim 1, wherein at least one of the walls of the housing has an elastic diaphragm.

8. A device as claimed in claim 7, wherein the elastic diaphragm is in the form of a rubber plate through which an electric cable leading to the microswitch is sealingly passed.

9. A device as claimed in claim 8, wherein the rubber plate forms one end wall of the housing and a setscrew, a flxing bolt for the bimetallic means and the passage for the electric cable are provided in said rubber plate.

10. A device as claimed in claim 8, wherein the microswitch means in the region of soldered joints for the electric cable is cast in a dielectric synthetic resin material.

11. A device as claimed in claim 1. wherein at least the bimetallic means and the microswitch means are mounted on a slide member which snugly fits the housing.

12. A device as claimed in claim 11, wherein the slide member is retained in the housing by a rubber plate forming one of the walls of the housing. 

1. An adjustable thermostat device for refrigerators or the like comprising a closed housing; elongated bimetal means fixedly mounted at one end thereof in said housing; a weight attached to said elongated bimetal means spaced from one end of the latter; microswitch means arranged in said housing and having an operating portion adapted to be engaged by said bimetal means intermediate the ends of the latter so as to be actuated during curving of said bimetal means under the influence of temperature variations; and means mounting said housing turnably about an axis extending transverse to the elongation of said elongated bimetal means so that the component of said weight influencing the curvature of said bimetal means may be varied depending on the turned position of said housing, whereby the temperature at which said microswitch means is actuated may be varied by turning said housing about said axis.
 2. A device as defined in claim 1, wherein said bimetal means comprises at least one elongated resilient bimetallic strip fixedly attached at one end thereof to said housing and carrying said weight on the other end thereof.
 3. A device as claimed in claim 2, wherein several bimetallic strips are held together by a sleeve so as to be relatively movable in their longitudinal direction, one of said strips projecting beyond the other bimetallic strips and connected at its other end to the weight.
 4. A device as claimed in claim 2, wherein a setscrew is arranged for cooperation with the resilient bimetallic strip and said strip is bent at the attachment end.
 5. A device as claimed in claim 4, wherein the setscrew with its end remote from the bimetallic strip is nonrotatably held in a rubber plate forming one of the housing walls.
 6. A device as claimed in claim 1, wherein the housing is of watertight and airtight construction.
 7. A device as claimed in claim 1, wherein at least one of the walls of the housing has an elastic diaphragm.
 8. A device as claimed in claim 7, wherein the elastic diaphragm is in the form of a rubber plate through which an electric cable leading to the microswitch is sealingly passed.
 9. A device as claimed in claim 8, wherein the rubber plate forms one end wall of the housing and a setscrew, a fixing bolt for the bimetallic means and the passage for the electric cable are provided in said rubber plate.
 10. A device as claimed in claim 8, wherein the microswitch means in the region of soldered joints for the electric cable is cast in a dielectric synthetic resin material.
 11. A device as claimed in claim 1, wherein at least the bimetallic means and the microswitch means are mounted on a slide member which snugly fits the housing.
 12. A device as claimed in claim 11, wherein the slide member is retained in the housing by a rubber plate forming one of the walls of the housing. 